The intrinsic ability of the shelves of the secondary palate to move from a vertical to a horizontal plane in the oral cavity is postulated to result from differential distribution and behavior of palatal shelf components. These components include epithelial cells and basal lamina, mesenchymal cells and a variety of extracellular molecules. Experiments will be undertaken to evaluate this postulate and to identify the activities and interrelationships of palatal shelf components that are responsible for shelf reorientation. In vitro elevation behavior and patterns of cell distribution will be investigated in shelves under various circumstances. Digitization of the x, y coordinates of each epithelial or mesenchymal cell coupled with trend surface analysis will detect the patterns of cell displacement occurring during in vitro elevation of shelves subjected to specific perturbations. These patterns will be compared to those seen during elevation of untreated shelves. Light and electron microscopic studies aimed at detecting localized changes in epithelial basal cell distribution, occurrence and orientation of microfilaments within them, and relationship of mesenchymal cells to the basal lamina during the course of in vitro elevation will also be conducted. Finally, radiolabelling and autoradiography will be used to determine if regional differences in the deposition of glycosaminoglycans occur at the epithelial-mesenchymal interface prior to shelf elevation which correlate with localized epithelial cell behaviors observed during reorientation.